Researchers compared the use of antidepressants among mothers of children with and without ASD. They found that those who had taken selective serotonin reuptake inhibitors (SSRIs) were more than twice as likely to have a child with an ASD diagnosis.

Autism spectrum disorder was uncommon in both groups, and the finding does not prove that SSRI use directly contributed to the children's ASD.

"This is the first study that has shown a possible association between SSRI use and autism and the findings should be considered preliminary," study researcher Lisa A. Croen, PhD, tells WebMD, adding that more research is needed to confirm an association.

WebMD called Pfizer and GlaxoSmithKline, makers of some of the SSRI antidepressants, for comment on the study. Pfizer did not respond before publication time. A spokeswoman for GlaxoSmithKline said the company would not comment because it had not yet had the opportunity to review the new study.

There has been a huge increase in the diagnosis of autism and related disorders in recent decades. While increased understanding and diagnosis of these conditions may explain the increase, there is also concern that as-yet unidentified environmental influences may be causing more children to develop ASD.

Antidepressant use among women in their childbearing years, especially use of SSRIs, has also increased dramatically in recent decades.

In an effort to investigate whether fetal exposure to antidepressants contributes to ASD risk, Croen and colleagues with the research arm of the California-based managed care group Kaiser Permanente examined the medical records of around 300 children with ASD and their mothers.

These records were compared to those of just over 1,500 children without an autism spectrum disorder.